1. Field of the Invention
The present invention relates to a self-inflating system for a tire of an automotive or other vehicle, and more particularly to a system in which the tire is automatically inflated from a high pressure reservoir in response to a sensed low pressure condition in the tire, and the high pressure air in the reservoir is also automatically replenished.
2. Description of the Related Art
Low tire pressure is an important cause of excessive fuel consumption, tire wear and impaired steerability. A normal tire will typically leak on the order of 25 percent of its pressure per year due to its inherent permeability. It is thus good practice to maintain tire pressure on a regular basis.
However, even checking tire pressure every few weeks may not prevent these adverse affects when a slow leak is present, and the leak may go undetected unless a careful record is maintained of how frequently the pressure in each tire has to be replenished. A fast leak or flat condition can rapidly cause damage to the tire and even render it unusable in a short period of time, but this condition may go unnoticed by an inexperienced driver until it is too late.
It is thus highly desirable to have some mechanism that automatically replenishes the tire pressure when it is too low. One such system is disclosed in U.S. Pat. No. 4,067,376 to Barabino. This patent incorporates a high pressure reservoir into the vehicle wheel, and uses a valve that automatically opens a passageway between the high pressure reservoir and the tire in response to the tire pressure falling below a selected threshold level.
In a prior art system of the type disclosed by Barabino, the high pressure air reservoir becomes progressively depleted as the air stored therein is used for maintaining full inflation of the tire. For this reason, the reservoir must be filled at intervals ranging from several months to a year or more depending on the size of the reservoir and the condition and use of the tire. This is disadvantageous in that a service operation for replenishing air for the tire is still required. A driver who neglects to check tire pressure will most likely also neglect to fill the reservoir, and the tire will begin to lose pressure when the air supply in the reservoir drops below a minimum level.